U.S. Secretary of State John Kerry says international sanctions on Iran could start to be lifted in as soon as six months.

"There are certain things that Iran needs to do and the [International Atomic Energy Agency] needs to do, and those things have to be resolved -- all of them -- before the sanctions begin to be relieved," Kerry told Voice of America's Persian News Network in an exclusive interview on July 20.

"So you're looking at somewhere about six months or so. It's hard to say exactly. It depends on what happens," Kerry said. "But I don't think there will be much felt before that."

Kerry went on to highlight some of the benefits Iran could expect to see in the event the nuclear deal that was worked out earlier this month between Iran and six world powers is formally approved and fully implemented.

"The people of Iran are going to see an improved standard of living. They’ll see sanctions lifted off of them that have prevented commerce, trade, travel, investment, all these other things," he said.

Referring to long-standing restrictions on U.S. trade with Iran, Kerry noted that the "primary embargo remains in place." But he listed "specific sanctions on finance, on banking, on the movement of goods" among those that could be lifted quickly.

"Foodstuffs will be allowed to be sold from Iran -- pistachios, carpets, other foodstuffs -- those things will be able to be sold," Kerry explained.

Iran and the UN Security Council's five permanent members -- Britain, China, France, Russia, and the United States -- plus Germany announced the deal to curb Tehran's nuclear program in exchange for sanctions relief in Vienna, Austria, on July 14.

But before the sanctions are lifted, a number of events outside Iran also must take place.

In particular, the U.S. Congress has 60 days to vote on the deal, and disapproval could provoke a prolonged veto battle with President Barack Obama. The U.S. State Department announced on July 19 that it had sent the Iran deal for congressional review.

Kerry suggested to VOA that the future of the deal should soon become clear.

"September will be the critical moment when people will begin to learn whether or not in fact this [deal] will be implemented," he said.

Addressing critics of the deal in Congress -- particularly among Republicans -- Kerry said that "some of them had opposed it before they read it."

"Many of them admitted they hadn’t read the deal when they started opposing it," he said. "Some people just oppose the idea of doing a deal with Iran."

Kerry said he was "glad" that Congress has 60 days to review the agreement because it would give time for U.S. lawmakers to reflect and see the benefits of the deal.

"I think when people really look at what is gained here, when they see that this is a possibility of actually doing away with a potential of a nuclear weapon and of perhaps opening up the possibilities of other good things happening, of a new relationship, I think people will see the benefit of it," Kerry said.

He warned that if Congress doesn't approve the deal, the alternative "could be choosing conflict and war."

"Because if we don't have this agreement, then I believe the ayatollah [Supreme Leader Ayatollah Ali Khamenei] would say: 'Why should I negotiate with these guys? They haven't delivered. They don't do it,'" Kerry said. "Why would our colleagues in the world support the sanctions when they say: 'The sanctions were supposed to be to get an agreement, but they got one and now they walked away?'"

In remarks to the nation on July 18, Khamenei said the nuclear deal would not change Tehran's policy toward the "arrogant" government of the United States.

Kerry described the supreme leader's remarks as "pretty negative and pretty dramatic." But he said he was an optimist in global affairs and believed that "what you hear today you may not hear in two months or 10 months or whatever."

Asked about the global community's concerns about human rights issues in Iran, Kerry said that the United States "will never stop believing in democracy and in people’s rights, human rights, and always stand for that."

Kerry argued that the United States didn't have time to discuss "any number of issues" with Iran during the negotiations, held amid the threat of "a nuclear arms race in the entire region."

"So we took a priority, we focused on the priority, we eliminated the potential of conflict over the nuclear weapons, providing it is accepted by Congress, accepted by the Majlis (the Iranian parliament), and implemented," Kerry said. "If that happens, the world will be a safer place."

Based on a July 20 interview conducted in Washington by Voice of America's Persian News Network